Improvement in air-engines



UNITED STATES PATENT OFFICE.

STEPHEN VILGOX, JR., GF I/VESTERLY, RHODE ISLAND.

IMPROVEMENT IN AIR-ENGINES.

Specification forming part of Letters Patent N0. 50,061, dated September19, 1865; antedated September 9, 1865.

To all whom it may concern:

Be it known that I, STEPHEN WILcoX, Jr., of Westerly, in the county ofWashington and State of Rhode Island, have invented cert-ain new anduseful Improvements in Hot-Air Engines; and Idohereby declare that thefollowingvis a full and exact description thereof.

The accompanying drawings form a. part of this specification.

Figure l is a side elevation, partly in section. Fig. 2 is a plan view.

Sixnilarletters of reference in dicatelike parts in both the drawings.

My improvements are applicable to a great variety of constructions. Theyrelate chiefly to the regulation and equalization of the temperature andpressure in the furnace and in the working parts ot' the engine. Bytheir aid. an engine may be subjected to great and sudden variations inthe load and to greatirregularities in the fire without endangering thedestruction ot' any parts by overheating' or experiencing any greatvariations in the rate of working'.

Means have been representedin some of myV prior patents for regulatingthe temperature and pressure by the expansion of mercury or other uidinclosed in a manner analogous to that adapted in thermometers. Theaction of such device is too slow. My present invention regulatesrapidly and is far more effective.

To enable others skilled in the art to make and use my invention, I willproceed to describe its construction and operation by the aid of thedrawings and of the letters of reference marked thereon.

A is the main cylinder, and a the main pis-.

ton. The latter is made of great depth, with a packing at the upper edgeand non-conducting material in the lower part, as usual.

B is a heater or furnace, into which the air is forced by a powerfulcompressing-pump, a.

The several main working parts in the engine are connected together andoperate each other in the obvious manner.

The main shaft D receives a rotary motion and thc piston e2 of thecompressing-pump e receives a reciprocating motion from the verticalreciprocations of the main piston c through the agency of the stoutrocking shaft E, with its arms E E2 and the several connecting rodsorlinks represented. The airispurnped or forced into the furnace B, andis there heated and expanded, after which it flows through a pipe, b',to the valve-chest b2, and from thence, on the lifting of theinduction-valve I at the proper time, it ilows into the main cylinder A,below the working-piston a, and forces it up. Before the completion ofthe upstroke the induction-valve I closes, and when the upstroke iscompleted the air below the piston c is discharged freely into theatmosphere through an eduction-valve. (Notrepresented.) Thisallows thepiston a to descend without resistance, after which the round ofoperation is repeated. Each reciprocation ofthe main piston a compels acorresponding reciprocation of the com pressing-piston a2, at eachascent of which air is drawn freely from the atmosphere through theinhaling-valve F, and at each descent the air previously inhaled isexpelled through the delivery-valve G, and thence through the passageHand oneor both the connecting-passages h ILZ into the furnace B, theportions of the air which shall pass through the respective passages hh2 being determined by the position of the slide-valve g, which isbalanced by the weight g', and is adapted to be very easily moved byturning the lever e.

My invention makes the pressure in the engine correspond to theresistance by automatically varyiug the temperature of the air to suitthe variations ofthe load. The means by which I effect this is asfollows: A small piston, t, is mounted in a vertical cylinder, T, thelower end of which is connected with the passage H by means of theaperturej. This piston t is adapted to move tightly and easily in itscylinder, and is Weighted by a lever, t', which is connected by a rod,t2, to the lever c. Whenever the pressure in the passage H exceeds theproper amount the piston t is forced up by this pressure, and 4byraising the lever t' and the connection t2 and lever e it depresses thesliding valve g and closes, or partly closes, the passage h, throughwhich the air from H is admitted beneath the grate, and opens wide thepassage h2, through which the air from H is admitted above there. Theconsequence of this change is that so much moreI air is admitted abovethe lire and so much less is admitted below to rise through the fuel andproso that the pressure is reduced below'the proper point, the piston tsinks and the slide-valve g rises, thus admitting more air below thegratev to come in contact with the fuel and support the combustion.

The action of this apparatus is very rapid. The instant the pressurerises above or sinks below the proper point it causes a correspondingmovement of the piston t. There is necessarily some friction onl anytightly-packed piston; but this friction may by proper care be mademoderate in amount. There isin my engine a fluctuation in the pressureat each stroke, which, although not sufficient under proper conditionsto induce an actual 'movement of the piston t up and down at eachstroke, is very nearly sufficient to do so, In other words, the frictionof the piston t and of the several parts connected thereto is almostovercome at each stroke by the variations ot' pressure in the furnaceandits connections accruing from the intermittent pumping in and usingout of the air. Now, a very little increase in the pressure above theordinary maximum in each revolution induces a movement of the piston tupward at the proper point in the revolution, and a very littlediminution ot' the pressure below the proper minimum induces acorresponding downward movement ofthe piston t at another point in therevolution. Thus the ordinary fluctuations of pressure at cach strokeaid in compelling the piston t to yield more readily to anyirregularities.

The toe m, iixed on the rock-shaft M, which is operated by an eccentric,as usual, tends to lift the induction-valve I to a uniform height ateachrevolution under all circumstances. The working of the shaft M nevervaries; but the motion which itimparts to the valve 1 is varied by asimple device now to be described A lever, fn, is mounted on thevalve-stein i by the aid ofthe pivot n. N is a movable fulcrum, adaptedto slide easily along the horizontal slot a: in the bracket X, therebycontrolling the motion ot' the valve I. At each upwardv movement of thearm m it lifts the outer end of the lever n, and the lever n, throughthe aid of the pivot n a-nd the fulcrum N, raises the valve-stem t', andconsequently opens the valve I, which remains open until the returnmovement of the toe mallows thelever a andits connection to descend; butthe height to which the valve I is raised, and consequently theeXtent-towhich the passage for the air into the working-cylinderA is open, variesaccording as the fulcrum N is moved along the slot w. When that fulcrumis moved away from the pivot n' the valve I is lifted higher, and whenthe fulcrum N is moved nearer to the pivot n the valve I is liftedfto aless extent at each'revolution. This device di'ers from a variablecut-off in the fact ythat it allows the valve Ito close at thesamejpoint in each revolution, whether the fulcrum N be in one positionor another.

The change in the position of the fulcrum N does not change the time ofopening or of closing the valve I, but only the extent of its opening.It has the effect to choke or throttle the current of air pastt-he valveI whenever the engine tends to run too fast. The fulcrum N is movedalong the horizontal slot by the action of a governor, R. The connectionis made by the bell-crank lever represented or by other obviousmeans,and the effect is to cause N to move to the left or toward thepivot n whenever the ily-balls lift too high in consequence of a toohigh velocity in the engine. Whenever the velocity gets too low and theballs ofthe governor sink the change induces a movement of the fulcrum Nin the opposite direction. Thus the adjustment of the position of thefulcrum N and the amount of throttling are determined automatically bythe action of the governor.

It is obviously possible to accumulate pressure in the furnace B and itsconnections to a dangerous extent. I provide against this by .the use ofa safety-valve peculiarly arranged in such manner as to insure itscertain and efficient action, and so as to become to some eX- tentaregulator of speed as well as pressure.

O-is the safety-valve, mounted on an aperture in the compressing-pistona2, and is held down thereon by its own gravity and by the tension ofthe coiled spring P. The total force holding this valve to its seat isso proportioned to the area of the passage o, which it covers, that thevalve shall be ordinarily held to its seat with a force just equal tothe maximum pressure which is intended to be carried in the furnace. Theforce which is due to the gravity of the valve itself is small comparedwith that due to the spring P; but by changing the weight of the valveand the stiffness of the spring the amount may be Varied to any desiredextent. l

The weight of the valve O performs an important function due to itsinertia. The piston 12,011 which it is mounted, reciprocates rapidly upand down. During the rst half of its descent it is increasing itsvelocity and during the last half it is decreasing its velocity. Thesedifferences of conditions render available the inertia of the valve 0 todiminish or increase the force with which it'is held to its seat atdifferent points of the stroke, and thus to facilitate its opening andclosing by aiding to overcome friction, stickiness, &c. During theearliest part of the descent of the piston a2 it is simply compressingthe air beneath it; but before it has reached its half-stroke the airbeneath it has been compressed to such extent that it commences to bedelivered through the valve G. Now, if the air is to escape at 1 allthrough the safety-valve O, it will com# "mence to do so at this point,and the piston not having yet slackened its speed, the valve EO-is notso firmly pressed to its seat as it is during the last half ot itsstroke. 'Ihis facilita-tes the opening at that point. It takes morepressure to open an ordinary safety-valve than it does to keep it openafter it is once raised,

and for that reason it is desirable to have the force holding the valveO to its seat less at this point than at a later period, to overcome thetendency to stick to its seat and the friction of the rubbing parts. Inshort, the inertia of the valve O, by causing it to press less iirmlyupon its seat during the first halt ot' its descent and press morefirmly during the last half, tends thereby to aid the valve in openingand closing at each stroke, and operates very effectuall y to prevcnttheaccumulation of pressure to any destructive extent in the apparatus.This peculiarity, by which the inertia ot' the mass is made available toboth open and close.

the safety-valve at the proper times, may not be very readilyunderstood, but mechanics will be able from the above to construct anduse the apparatus, and will be able, with attention, to see that theinertia of the mass O, by contributing to separate it (the safety-valve)from the piston a2 during the early portion oi' its downstrohe and tourge it to its seat during` the closing portion, tends to induce alii'tingof the safety-valve, and a consequent delivery ot' the airthrough the same during a short portion of each stroke, so soon as thepressure begins to be excessive. The period during which thesafety-valve will remain open increases as the pressurein the furnaceincreases, so as longer to resist the increasing tenuency to close; andas (unlike a safety-valve on a steam-boiler) it is never necessary todischarge all the tluid through this safety-valve, the apparatus is verydesirably secured against any too high pressure.

A further advantage ot' mounting the safetyvalve on the pump-piston is,that it becomes a regulator of speed as well as of pressure. The speedot' the piston is such that a weighted valve would be thrown from itsseat at every stroke. Now, by properly proportioning the opening,weight, and spring, a slight increase of speed above the normal pointwill cause the valve to rise without any increase of' pressure, thuspreventing the engine from racing under any circumstances.

It may be remarked that the devices previously described will ordinarilyavoid a necessity for blowing much air through the safetyvalve.

It will be observed that the cylindrical portion ot' my working-cylinderA is represented as formed ot very thin material. I employ in practicesheet-iron ot' the best quality and about one-sixteenth ot' an inchthick. This is preferable to cast-iron, not only on account of the smallcost of material and the slightlabor required in forming it, but also onaccount of its triiiing conduction of heat from the lower to the upperportion. I rivet it at its upper edge to a stout ring of cast-iron orother suitable material (indicated by A,) and at its lower edge to acorresponding ring, A, fixed in the brick-work. I perforate these ringsA A2 with vertical holes, as represented, and rivet to their exterior acorresponding case, A3, of very thin sheet-iron, (Russia iron, bypreference,) extending around the cylinder at a little distancetherefrom, and forming a mechanical protection against injuries to theinner or true cylinder. I secure these rings by means of rivetsconntersunk so as to present no projecting surfaces on the inside of thecylinder.

lThe space between the cylinder A and the exterior case, A3, is freelyventilated by the aid ot' the holes in the rings Ai and A2, cool aircoming in constantly through A2, and thesame iiowing out at a higher'temperature through the ring A.

I forni the compressing-cylinder a' in a similar manner to theworking-cylinder A, above described; but I do not deem it so importantto ventilate the space between the compressing-cylinder and itsinclosing-case.

I constructand arrange the valves F and G and their seats andconnections in a manner which allows them to be very cheaply and easilyiliade Iand to be very easily accessible for examination or repairs. Themode ot' doing this is indicated quite clearly in Fig. l. Each valve isformed with an iron or other rigid plate ot' an area a little largerthan the aperture which the valve is to cover, and with a sheet ot'leather', vulcanized rubber, or cloth, or other tiexible material. rIheseats ot' these valves are parallel to each othenand are easily preparedby planing,` or otherwise to any degree of nicet-y that may belrequired.

'Iue bonnet Q, heldin place by bnlrs, (not represented),1nay be veryreadily removed and applied. lts removal allows the valves F and G to bevery readily removed, and, returning it to its place and securing it bybolts, the valves F and G are tirmly and safely held.

Some ot' the advantages due to certain features ot my invention may beseparately enumerated as follows:

First. By reason ot' the fact that my sensitive apparatus t and itsconnections, by changes ot' pressure, operate the directing apparatus gso as to turn more or less air below the tire in the manner represented,I am able to rapidly raise and lower the temperature ot' the air, and tocorrespondingly change the vigor of the tire by the same simplemechanism, thus tending to kecp the pressure uniform for the time being,and preparing the re to maintain a persistence in that condition, it'necessary. I am able by this expedient to keep the temperature of theair in my apparatus at thelowestallowable point under all conditions,and this contributes to the durability of my engine. s

Second. By reason of my construction and arrangement ot' the parts N n am, adapted to raise the induction-valve I to variable heights and tolower it to its seat in uniform periods, I am able to throttle or chokethe admission of air from the furnace B to the working-cylinder A by theinduction-valve itself without worked Y varying the point of cut ott,and consequently Without much varying the terminal pressure. This avoidsany evil eifects to be apprehended from a partial vacuum at the endofthe stroke, is cheaper to construct than an additional throttle-valve,and is not liable to be choked like an ordinary throttle in such anengine, because on each lifting of the induction-valve I it clearsitself ot any ashes or cinders which may catch under it.

Third. By reason of the fact that my safetyvalve, openingoutward todischarge iiuid when the pressure accumulates, is mounted in thecompressing-cylinder a', and is carried vertically and rapidly on thepiston a? and held down upon its seat by the aid of the spring l?, I ainable to make itsinertia available to overcome the friction obstructing'its motion, and avoid the liability of its sticking down, and to aid inregulating the motion of the engine.

Fourth. By reason ot' the fact that` my cylinders A and a are of sheetmetal, I amable to construct them more cheaply, and to keep them coolerat the Lipper end, Where the packing is applied, and to make the enginemuch lighter.

Fifth. By reason of the fact that my protecltion A3 surrounds thesheet-metal cylinder A, with a free circulation of the external air through the space between, as represented, I am able epectually to protectthe thin metal from injury by any ordinary slight accident Withoutmaterially increasing the heat in the metal. v

Sixth. By reason ot' the fact that my valves G and F are mounted in themanner described on seats cast on the cylinder, as represented, and heldin place by the single bonnet Q in the manner shown, I am able toproduce and finish them easily Without labor in fitting, to savefastenings in holding the valves, and to gain easy access to the Wholeby the removal of a single part when desired.

Having now fully described my invention,4

.pose herein set forth.

3. Mounting the safety-valves O on the compressing-piston a2 of ahot-air engine, substantially as and for the purpose herein set forth.

4. Constructing the cylinder A or pump a', or both, of sheet metal, inthe manner and for the purpose herein set forth.

5. In connection with the last, the ventilated jacket or protection A3,constructed and arranged substantially in the manner herein set forth.

6. The Within-described arrangement ot' the bonnet Q and the valves Fand G, with their seats and passages cast on the cylinder, and arrangedsubstantially in the manner and for the purposes herein set forth.

STEPHEN lVILCOX, JR.

Witnesses:

W. H. ROBINSON, WILLIAM P. Gov.

